react-common/lib/services/isEmpty.test.ts

import * as fc from 'fast-check'
import isEmpty from './isEmpty'

describe('lib/services/isEmpty', () => {
  it('should exist', () => {
    expect(isEmpty).toBeDefined()
  })

  it('should be a function', () => {
    expect(isEmpty).toBeFunction()
  })

  it('should accept 1 argument', () => {
    expect(isEmpty).toHaveLength(1)
  })

  it('should return a boolean value', () => {
    fc.assert(
      fc.property(
        fc.anything(),
        v => {
          expect(typeof isEmpty(v)).toBe('boolean')
        }
      )
    )
  })

  describe('on arguments', () => {
    it('should return `true` on an argument with value of `undefined`', () => {
      expect(isEmpty(undefined)).toBe(true)
    })

    it('should return `true` on an argument with value of `null`', () => {
      expect(isEmpty(null)).toBe(true)
    })

    it('should return `false` on an argument with value that is neither `undefined` nor `null`', () => {
      fc.assert(
        fc.property(
          fc.anything().filter(v => typeof v !== 'undefined' && v !== null),
          v => {
            expect(isEmpty(v)).toBe(false)
          }
        )
      )
    })
  })
})